Muffler having depressed channel forming tuning passages



MUFFLER HAVING DEPRESSED CHANNEL FORMING TUNING PASSAGES Filed June 25, 1965 2. Sheets-Sheet 1 I NVENTOR.

far/M045" Oct. 5, 1965 P. F. JETTINGHOFF 3,209,858

MUFFLER HAVING DEPRESSED CHANNEL FORMING TUNING PASSAGES 2, Sheets-Sheet 2 Filed June 25, 1963 United States Patent O 3,209,858 MUFFLER HAVING DEPRESSED CHANNEL FORMING TUNING PASSAGES Paul F. .Iettingho Jackson, Mich., assignor to Walker Manufacturing Company, a corporation of Delaware Filed June 25, 1963, Ser. No. 290,500

16 Claims. (Cl. 181-54) This invention relates to a mutiler for silencing gases.

A muffler embodying the invention is particularly suited for automotive usage, especially to silence exhaust gases.

In the silencing of Iautomotive intake or exhaust gases, the lprinciple of th-e Helmholtz resonator, employing -a tuning chamber and a tuning tube, is often used to attenuate predetermined relatively low lfrequencies. IIt is the .object of the present invention to provide an improved tuning pass-age construction of such a nature that the effective length `of the tuning ypassage may be easily changed in different muillers even `though the parts used are identical.

Another object of the invention is to provide an improved tuning tube or passage of such .a nature that a broad banding effect (wider range of frequencies attenuated) is produced.

A further object of the invention is to provide a mutller in which two chambers tune off of opposite ends of a tuning passage.

According to the invention, an elongated depression 'with an opening therein is formed in the side of a gas ll-ow tube. An -elongated cap is secured to the outside of the tube to cover the opening .and a portion of the length of the depression .and thus acts with the depression to form la tuning passage. Broad banding is obtainable by forming louvers in the cap. The opening m-ay be located at an intermediate point in the channel so that chambers may be connected to opposite ends t att-enuate dilferent frequencies.

The invention is illustrated in the accompanying drawings in which:

FIG. 1 is a longitudinal cross section of a muffler embodying the invention;

FIG. 2 is a cross section along line 2 2 of FIG. l;

FIG. 3 is -a longitudinal cross section through another `form of muffler embodying a modified form of the invention;

FIG. 4 is a cross section along the line 4 4 of FIG. 3;

FIG. 5 is a longitudinal cross section through another modification of the invention;

FIG. 6 is a cross section along line 6 6 of FIG. 5;

FIG. 7 is a longitudinal cross section through a modication -of the invention; and

FIG. 8 is a cross section along the line 8 8 of FIG. 7.

The muliler 1 of FIGS. 1 and 2 is a design of maximum simplicity and minimum size and is well adapted for use in automotive exhaust systems developed by the assignee hereof wherein a multiplicity of small size silencing components are distributed over the entire length of the system. =In such usage the outer diameter of the shell 3 of muiller 1 would be no more than about four inches. In such case the length Iof the shell 3 will be suflicient to give the desired volume to internal chamber 5 so thlat it can be tuned to silence the desired frequency. A plurality of mulers 1, tuned to different frequencies, may be employed in an exhaust system.

The muffler 1 has a straight through ilow gas tube 7. The shell 3 is originally a cylinder of the diameter shown and the ends yare swaged down (compressed) to form inlet and outlet end -walls 9 'and 1'1 and inlet and outlet necks 13 and 15 which iit tightly around the tube 7 and 3,209,858 Patented Get. 5, 1965 ICC are spotwelded to it, the ends of theY tube serving as the inlet and outlet bushings 17 and 19 for the muffler 1.

Prior to assembly with shell 3, a radial slit 211 is made in the wall of the tube 7 .and commencing at the slit a longitudinal depression or channel 23 is formed in the wall of the tube, this terminating in a closed end section 25. Depression of the tube wall at the slit 2.11 forms an opening `27 which lies in a radial plane and which connects the inside of the t-ube 7 with the outside along the channel 23. Commencing at the end of channel 23 having opening 27, a portion of the channel length is covered by Ian elongated cap 29 which fits on the out-side of tube 7 and is welded to it as shown by the Xs. The cap 29 does not extend lthe full length of channel 2'3 so that there is a space 31 between the open end 3-3 of the cap and the closed end 25 of the channel, the space 31 opening into or being a part of the chamber 5.

It will be seen that along the length that they are coextensive the channel 23 'and the cap 29 form a tuning tube or passage 35 connecting the inside of tube 7 to the chamber 5 and that this passage is the only means of communication between the tube and the chamber. The length of passage 35 affects the tuning of the mutller (the frequency it attenuates) and it will be seen that this can be easily varied with the identical parts by positioning the .cap to the left in FIG. 1 so as to shorten the length of passage 35.

In mufller 1 the inlet 27 to the tuning passage 35 is at the'upstream end. The embodiment of FIGS. 3 4 shows the opening at the downstream end and also shows the tuning passage of this invention embodied in a muler construction typical of the kind used in current model U.S. automobiles In FIGS. 3-4, the muffler 101 has an outer shell 103 with end headers and 107 at the inlet and outlet ends. lInternal transverse partitions 109, 11d, 113, and 115 divide the shell 103 into chambers 117, 119, 121, 123, and 125. An inlet tube `127 is supported in llanged necks in the header 105 and in partitions .109, 1-11, and 113. An outlet tube `129 is supported in flanged necks in partitions 1,11, 1\13, and 1115, and in outlet header 107. A return flow tube 1311 is supported in flanged necks in partitions 111 and 11.3. Inlet tube 127 is louvered in chamber 121 but the louvers are covered by a shell 133 to form a high frequency and roughness attenuating spit chamber 135. Outlet tube 4129 is louvered in chambers 1.21 and which therefore a-ct as spit chambers. Return llow tube 131 is also louvered in chamber 121 to provide spit chamber attenuation and permit som-e cross bleeding to tube 129. Gas enters the m-ulller 101 through tube 127, empties into and reverses flow in crossover chamber 123, ilows back through tube .131, and crosses over in chamber 119 to outlet tube 129 through which it flows out of the muffler.

The portion of inlet tube 127 within chamber 117 is provided with a tuning passage similar to passage 35. Thus, the Wall of tube 127 is slit at 137 and depressed to form channel 139. A cap 141 tits on the wall of the tube 127 and is welded to it to form tuning passage 143 that communicates at its downstream opening 145 with the inside of tube 127 and at its upstream opening 147 with the chamber 117. By positioning the cap 141 to the left or right on tube 127 the length of the tuning passage 143 could be adjusted to vary the frequency to which the chamber 117 and passage 143 are tuned to attenuate. In the muffler 101, the chamber 117 will silence lower frequencies than any of the other chambers.

The frequency range attenuated by the passage 143 and chamber 117 can be broadened (broad banded) or the attenuation curve smoothed out by providing louvers 149 in the cap 141. The louvers will also act individually to remove some high frequency noise since they act as short tuning tubes. Holes may be used instead of louvers in the cap 141 for broad banding but the louvers are preferred. This principle of broad banding by means of louvers or holes maybe used in the ordinary cylindrical tuning tube structure of conventional resonator chamber construction in muiiiers. It may be used on all caps or tuning passage walls shown herein.

It will be noted that the channels 23 and 139 will reduce the cross sectional area of their respective gas flow tubes and give a restrictor effect for sound attenuation and sound energy loss. While this should increase back pressure slightly, tests to date have shown, oddly, that back pressure is lowered slightly.

In FIGS. 5 and 6, the muffler 201 has a shell 203 with a gas flow tube 205 that has a channel 207 depressed therein. In this case the ends of the channel 207 are closed but an opening 209 is provided in the sidewall of the tube at an intermediate point in the length of the channel. A channel covering cap 211 is attached to the tube 205 over the opening 209 and extends in opposite Vdirections for different distances from the opening to vprovide two different length tuning passages 213 and 215 which form the only inlets and outlets to closed chamber' 217. Thus, chamber 217 is tuned to two different frequencies.

In FIGS. 7 and 8, the muiiier 301 has a shell 303 with a gas flow tube 305 that has a channel 307 depressed therein. The ends 0f channel 307 are closed but it has an opening 309 at an intermediate point. A channel covering cap 311 is attached to the tube 305 over the Opening 209 and extends different distances in opposite directions to form a long tuning passage 313 and a short tuning passage 315. As noted in FIG. 8, the tube 305 may be depressed down in such a way that the cap its into the recess and is of the same diameter as the tube. Thus, the cap and tube readily pass through a round anged neck 317 in a partition 319 that divides the inside of shell 303 into a large closed chamber 321 communicating with long passage 313 and a 'small closed chamber 323 communicating with short passage 315. Thus, the passage 313 and chamber 321 are tuned to attenuate a low frequency and the passage 315 and chamber 323 are tuned to attenuate a higher frequency.

Louvers or openings may be provided in the caps 211 or 311 over one or both of the tuning passages to give a broad banding effect.

Modifications may be made in the structure shown herein by way of illustration without departing from the spirit and scope of the invention.

I claim:

1. A muiiier comprising a casing, a gas flow tube running through said casing, said tube having a wall with a longitudinally extending channel formed therein, said tube having an opening at one end of said channel for communication of said channel with the inside of said tube, a cap attached to the outside of said tube and covering said opening and a part of the length of said channel and acting with said -channel to form a tuning passage, the volume of the space in said casing around said tube and the length of said tuning passage being selected to silence a predetermined frequency, a plurality of perforations along the length of said cap to provide broad banding of the frequencies attenuated by said passage and said volume.

2. A muiiier comprising a casing, a gas flow tube running through the casing, said tube having a wall with a longitudinally extending channel for-med therein, said tube at one end of the channel having an opening communicating said channel with the inside of the tube, a cap attached to the outside of the tube and covering said opening and a part of the length of said channel and the length of said a predetermined frequency, and louvers formed in said cap to provide broad banding of the frequencies attenuated by said passage and space.

3. In a muiier having a shell, a gas flow passage extending through said shell, said shell and said gas flow passage forming a chamber therebetween, tubular means open at one end to said gas flow passage and at its other end to said chamber and forming the only inlet and outlet to said chamber, the length of said tubular means and the volume of said chamber being selected to tune the chamber to silence a predetermined frequency, said tubular means having a wall provided with a plurality of perforations along its length to broad band the attenuation of said chamber.

4. The invention set forth in claim 3 wherein said perforations comprise louvers in the wall of said tubular means.

5. In a muffler for attenuating sound in a gas, a shell having a closed chamber therein, a gas ow tube passing through said chamber, said tube having a wall with a longitudinally extending inwardly depressed channel substantially straight throughout its length formed therein and facing said chamber, said channel extending substantially coaxially with said tube, said wall defining an inlet opening in an intermediate portion of said channel connecting said intermediate portion with the inside of said tube, and a longitudinally extending cap atiixed to said tube, said cap extending substantially coaxially with said tube over only a portion of the length of said channel in opposite directions from said opening, said cap terminating short of each end of said channel to form separate outlet openings at each end thereof between said channel and said chamber, said cap, said channel and said inlet opening forming two separate tuning passages between the inside of said tube and said chamber.

6. The invention set forth in claim 5 wherein said cap extends further in one direction from said opening than in the other whereby said two tuning passages are of different lengths.

7. In a muflier for attenuating sound in a gas, a shell having a closed chamber therein, a gas flow tube passing through said chamber, said tube having a wall with a longitudinally extending inwardly depressed channel formed therein in said chamber, said wall having an opening connecting an intermediate portion in the length of .said channel with the inside of said tube, a cap attached to said tube over a part of the length of said channel and extending in opposite directions from said opening to form two tuning passages, said cap terminating short of each end of said channel whereby said channel and said cap form two separate tuning passages, partition means in said shell in radial alignment with a part of the length of the cap and dividing said closed chamber into two separate sections communicating only through the two tun-ing passages formed by the cap and channel.

8. The invention set forth in claim 7 wherein said cap extends further in one direction from said opening than rin the yotherwhereby said two tuning passages are of different lengthsand whereby said two separate chamber sections are tuned to attenuate different frequencies.

9. In a muiiler for attenuating sound in a gas, ashell having a closed chamber therein, a gas iiow tube passing axially through said chamber, said tube having a side wall in said chamber with an Opening therein, a cap attached to the tube over said opening and extending axially along tube in opposite directions from said opening, said cap being spaced from the wall of said tube and defining with said wall two tuning passages extending in opposite axial directions, openings at each end of said Cap between said tuning passages and said chamber and forming the only inlets and outlets to said chamber, and a plurality of perforations formed by the portion of the wall of said cap defining at least one of said tuning passages to provide broad banding.

10. In .a muflier for kattenuating sound in a gas, a shell having a closed chamber therein, a gas flow tube passing through said chamber, said tube having a wall with a longitudinally extending inwardly depressed channel formed therein in said chamber, said wall having an opening connecting an intermediate portion in the length of said channel with the inside of said tube, a cap attached to said tube over a part of the length of said channel and extending in opposite directions from said opening t form two tuning passages, said cap terminating short of each end of said channel whereby said channel and said cap form two separate tuning passages, said cap having a plurality of perforations along at least a portion of its length to broad band the frequency attenuation of said chamber.

11. The invention set forth in claim wherein the cap is perforated by means of louvers formed therein.

12. In a muffler for attenuating sound in gas, a shell, a transverse partition dividing said shell into two longitudinally adjacent closed chambers, a gas flow tube passing through both chambers, said tube having a side wall with an opening therein, a cap attached to the tube over said opening and extending longitudinally of the tube in opposite directions from said opening, said cap being spaced from the wall of the tube and defining with said wall two tuning passages extending in opposite directions, one of said passages opening at its end into one of said chambers and the other opening at its end into the other of said chambers, both said passages communicating with the inside of the tube through said side wall opening.

13. The invention set forth in claim 12 wherein said tuning passages are of different lengths.

14. The invention set forth in claim 12 wherein said chambers are of different volumes.

15. The invention set forth in claim 12 wherein said tuning passages are of different lengths and said chambers are of different volumes and the longer of said passages opens into the larger of said chambers whereby such chamber is tuned to attenuate a lower frequency than the other passage and chamber.

16. The invention set forth in claim 12 wherein the wall of the cap forming at least one of said passages is perforated to broad band the attenuation of the passage and chamber into which it opens.

References Cited by the Examiner UNITED STATES PATENTS 2,056,608 10/36 Jack. 2,075,265 3/37 Bourne 181-59 2,099,858 11/37 MacKenzie et al. 181-48 2,124,933 7/ 38 Starkweather 181-48 2,166,670 7/ 39 Martin. 2,182,204 12/39 Hector 181-54 2,251,880 8/41 Cary et al 181-48 2,323,955 7/43 Wilson 181-48 2,357,791 9/44 Powers 181-54 2,580,564 1/52 Ludlow 181-59 X 2,652,128 9/53 Cary 181-54 2,950,777 8/ 60 Deremer 181-54 FOREIGN PATENTS 994,851 8/51 France.

LEO SMILOW, Primary Examiner. 

3. IN A MUFFLER HAVING A SHELL, A GAS FLOW PASSAGE EXTENDING THROUGH SAID SHELL, SAID SHELL AND SAID GAS FLOW PASSAGE FORMING A CHAMBER THEREBETWEEN, TUBULAR MEANS OPEN AT ONE END TO SAID GAS FLOW PASSAGE AND AT ITS OTHER END TO SAID CHAMBER AND FORMING THE ONLY INLET AND OUTLET TO SAID CHAMBER, THE LENGTH OF SAID TUBULAR MEANS AND THE VOLUME OF SAID CHAMBER BEING SELECTED TO TUNE THE CHAMBER TO SILENCE A PREDETERMINED FREQUENCY, SAID TUBULAR MEANS HAVING A WALL PROVIDED WITH A PLURALITY OF PERFORATIONS ALONG ITS LENGTH TO BROAD THE ATTENUATION OF SAID CHAMBER. 